Study of the decay of hot nuclei formed inLa139-induced reactions atEA=45MeV by a hybrid dynamical-statistical calculation

Abstract

The reactions {sup 139}La + {sup 27}Al and {sup 139}La + {sup 65}Cu at {ital E}/{ital A} = 45 MeV have been modeled by combining a Boltzmann-Nordheim-Vlasov dynamical model calculation with a statistical sequential binary decay model code. For the reaction {sup 139}La + {sup 27}Al, the major features of the experimental data are adequately described by the model calculations. These features include the inclusive fragment cross sections and the total charge and source velocity distributions of multiple fragment events. Other finer features, such as charge-Dalitz plots and the branching ratios between events of different multiplicity, are not reproduced by the calculation. The failure of the calculations is even greater for the reaction {sup 139}La + {sup 65}Cu, in which only the source velocity distributions of multiple fragment events are reproduced. Because the source velocity can be a measure of how much of the target is incorporated into the projectile in inverse kinematics reactions, this suggests that the earliest stages of the reaction, described by the dynamical calculation, are adequately characterized by the model. It is the later stages of the reaction, when fragments are emitted, where the model calculation appears to fail. However, there are some indications that statisticalmore » decay in the reaction {sup 139}La + {sup 65}Cu has occurred, whether by sequential binary decays or some type of prompt multifragmentation. {copyright} {ital 1996 The American Physical Society.}« less